Atrial fibrillation detected after stroke is related to a low risk of ischemic stroke recurrence

Objective To compare the risk of 1-year ischemic stroke recurrence between atrial fibrillation (AF) diagnosed after stroke (AFDAS) and sinus rhythm (SR) and investigate whether underlying heart disease is as frequent in AFDAS as it is in AF known before stroke (KAF). Methods In this retrospective cohort study, we included all ischemic stroke patients admitted to institutions participating in the Ontario Stroke Registry from July 1, 2003, to March 31, 2013. Based on heart rhythm assessed during admission, we classified patients as AFDAS, KAF, or SR. We modeled the relationship between heart rhythm groups and 1-year ischemic stroke recurrence by using Cox regression adjusted for multiple covariates (e.g., oral anticoagulants). We compared the prevalence of coronary artery disease, myocardial infarction, and heart failure among the 3 groups. Results Among 23,376 ischemic stroke patients, 15,885 had SR, 587 AFDAS, and 6,904 KAF. At 1 year, 39 (6.6%) patients with AFDAS, 661 (9.6%) with KAF, and 1,269 (8.0%) with SR had recurrent ischemic strokes (p = 0.0001). AFDAS-related ischemic stroke recurrence adjusted risk was not different from that of SR (hazard ratio 0.90 [95% confidence interval 0.63, 1.30]; p = 0.57). Prevalence of coronary artery disease (18.2% vs 34.7%; p < 0.0001), myocardial infarction (11.6% vs 20.5%; p < 0.0001), and heart failure (5.5% vs 16.8%; p < 0.0001) were lower in AFDAS relative to KAF. Conclusions The lack of difference in 1-year ischemic stroke recurrence between AFDAS and SR and the lower prevalence of heart disease in AFDAS compared to KAF suggest that the underlying pathophysiology of AFDAS may differ from that of KAF.